1. Field of the Invention
The present invention relates generally to a method of recognizing speech and, more particularly, to a method and apparatus for recognizing speech by measuring the confidence levels of respective frames.
2. Description of the Related Art
Machines, home appliances, and automation systems are conventionally controlled using the hands of persons. Recently, control technology using speech is being researched by industry as research into speech recognition is increasing. A system that controls and commands objects in homes, that is, a home network system or a home automation system, provides a Voice User Interface (VUI) function for speech recognition. In order to control home appliances using a natural language in home environments, it is necessary to detect keywords. In this case, keyword detection performance increases in proportion to accurate confidence calculation on keywords. The language of human beings does not coincide with a specific form or specific phonemes and are based on natural language, so that it is necessary to detect keywords from recognized speech.
Conventionally, confidence calculation for a single word or a single subword is performed based on the identical contribution of respective frames. In U.S. Pat. No. 6,539,353 B1, a recognized word is composed of subwords units. The confidence level of a word is determined based on values acquired by applying weights to the confidence levels of subwords that form a word. Different weights are applied to the subwords, so that the confidence level can be acquired in consideration of the influence of each subword on the confidence level. However, in U.S. Pat. No. 6,539,353 B1, the influence of the confidence levels for respective frames based on a subword unit is considered. Even the words of the same subword provide difference pieces information on a frame basis, but uniform calculation is performed without consideration of the difference. Accordingly, it is difficult to improve the accuracy of the measurement of confidence levels.